An objective circulation pattern classification for the region of svalbard

Abstract

Käsmacher, O. and Schneider, C., 2011. An objective circulation pattern classification for the region of Svalbard. Geografiska Annaler: Series A, Physical Geography, 93, 259–271. DOI: 10.1111/j.1468‐0459.2011.00431.x

Abstract

This study presents an automated or so‐called objective circulation pattern classification for the region of the Svalbard archipelago on the basis of gridded NCEP/NCAR‐reanalysis data in a spatial resolution of 2.5 × 2.5° for the variables sea level pressure and geopotential heights on the 500 and 700-hPa levels. Self‐organizing maps were set up and run several times, each time using a different number of clusters into which to partition the data. After evaluating the results for all clusters by means of statistical indices we decided to use nine circulation patterns for further analysis. The resulting patterns were related to surface variables for Svalbard in order to test how good the catalogue of circulation patterns performs as a tool for the analysis of synoptic forcing. Furthermore, the catalogue was compared to an alternative subjective classification of weather types which results in only partly coherence. We show that the different circulation patterns derived in this study nicely represent seasonal states of the atmosphere. Within seasons, significant deviations of surface air temperature and precipitable water content are associated with the different weather types. The latter fact points to a broad applicability of this circulation pattern classification for studies that address the impact of interannual atmospheric variability on other parts of the geo‐system such as glaciers, ice caps and vegetational patterns.

Key words:

• atmospheric circulation
• circulation pattern
• circulation types
• classification
• cluster analysis
• self‐organizing maps
• Svalbard

Acknowledgments

This work has been supported by grant No. SCHN 680/2‐1 of the German Research Foundation (DFG) within the International Polar Year 2007–08 (IPY) core projects GLACIODYN and KINNVIKA and grant No. 03F0623B of the German Ministry of Research and Education (BMBF) within the European Science Foundation (ESF) project SVALGLAC as part of the ESF call POLAR CLIMATE. We would like to thank Veijo Pohjola for thoroughly editing this paper. Furthermore, we thank the two anonymous reviewers for their valuable help in improving the manuscript.

Additional information

Notes on contributors

Oliver Käsmacher

Oliver Käsmacher and Christoph Schneider, RWTH Aachen University, Department of Geography, Division of Physical Geography and Climatology, Wüllnerstraße 5b, 52064 Aachen, Germany. E‐mail: [email protected]‐aachen.de